Log Message:
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[otlLib] Use Value.getEffectiveFormat() instead of .getFormat()
This changes some test expectations. They are mostly desired. But
I don't see why we are creating empty lookups in the failing test
Tests/feaLib/data/ZeroValue_PairPos_vertical.ttx, instead of no
lookup at all. So that needs figuring out to complete this change
and then update expectation.